CVE-2025-3052: Microsoft UEFI Firmware RCE Vulnerability

CVE-2025-3052 Overview

CVE-2025-3052 is an arbitrary write vulnerability in a Microsoft-signed Unified Extensible Firmware Interface (UEFI) module. The flaw lets an attacker control a write operation, leading to arbitrary memory writes that include modification of critical firmware settings stored in Non-Volatile Random-Access Memory (NVRAM). Because the affected module carries a valid Microsoft signature, it can load on Secure Boot-enabled systems. Successful exploitation enables Secure Boot bypass, persistent pre-OS implants, and full system compromise below the operating system trust boundary.

Critical Impact

An authenticated local attacker can tamper with NVRAM variables and bypass UEFI Secure Boot, establishing firmware-level persistence that survives operating system reinstalls.

Affected Products

• Microsoft-signed UEFI firmware modules trusted under the Secure Boot allow list
• Systems that ship with the vulnerable signed module in their firmware volume
• Endpoints relying on UEFI Secure Boot to enforce pre-OS code integrity

Discovery Timeline

• 2025-06-10 - CVE-2025-3052 published to the National Vulnerability Database (NVD)
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-3052

Vulnerability Analysis

The vulnerability resides in a Microsoft-signed UEFI application that performs an unvalidated write using attacker-influenced input. UEFI firmware executes in System Management Mode-adjacent privilege before the operating system loads. Because the signed binary is trusted by the Secure Boot db database, the Boot Manager loads it without rejecting its image hash. The arbitrary write primitive enables modification of any address in pre-boot memory, including the global gSecurity and gSecurity2 function pointers and NVRAM variables such as PK, KEK, db, and dbx.

An attacker who alters these variables disables image verification on subsequent boots. The result is execution of unsigned bootloaders, kernel drivers, or implants that persist across operating system reinstallation. The exploitation surface is local, but the impact crosses the firmware-to-OS trust boundary, producing a scope change reflected in the high integrity and confidentiality ratings.

Root Cause

The signed UEFI module accepts an externally controllable pointer and length, then writes to that destination without bounds or destination validation. The image carries a Microsoft third-party UEFI Certificate Authority signature, so revocation requires updating the Secure Boot dbx forbidden signatures database to reject the vulnerable binary hash.

Attack Vector

A local attacker with administrative privileges stages the signed vulnerable binary on the EFI System Partition (ESP) and configures the boot order or BootNext variable to execute it. On the next reboot, the firmware loads the trusted image, the attacker-controlled write primitive executes, and NVRAM Secure Boot variables are overwritten. Subsequent boots then accept attacker-supplied unsigned code. Refer to the Binarly Security Advisory BRLY-DVA-2025-001 and CERT Vulnerability ID 806555 for module-specific exploitation details.

Detection Methods for CVE-2025-3052

Indicators of Compromise

• Unexpected entries on the EFI System Partition referencing the vulnerable signed binary hash listed in BRLY-DVA-2025-001
• Modifications to PK, KEK, db, or dbx NVRAM variables outside of firmware update windows
• Changes to BootOrder, BootNext, or Boot#### variables pointing to non-vendor loaders
• Secure Boot reported as disabled or in Setup Mode on systems that previously enforced it

Detection Strategies

• Compare measured boot Trusted Platform Module (TPM) PCR[0] and PCR[7] values against known-good baselines to identify firmware and Secure Boot policy drift
• Use UEFI firmware integrity tools such as CHIPSEC to enumerate loaded drivers and validate NVRAM variable contents
• Hunt for the vulnerable binary hashes published in the Binarly advisory across managed endpoints

Monitoring Recommendations

• Forward Windows Microsoft-Windows-TPM-WMI and Measured Boot logs to a central data lake for baseline analysis
• Alert on administrative writes to \EFI\ directories on the ESP from non-update processes
• Track mokutil --sb-state and bcdedit output across the fleet to identify Secure Boot state changes

How to Mitigate CVE-2025-3052

Immediate Actions Required

• Apply the latest dbx Secure Boot revocation update from Microsoft and OEM firmware vendors to block the vulnerable signed binary
• Restrict administrative access on endpoints, since the attack vector requires high local privilege to stage the binary and modify boot variables
• Validate Secure Boot is enabled and enforced after applying the revocation update

Patch Information

Microsoft has revoked the vulnerable signed module through the Secure Boot forbidden signatures database (dbx). Deploy the updated dbx payload through Windows Update on Windows systems and through fwupd or vendor tooling on Linux systems. Consult the UEFI Specification Section 32 for revocation mechanics and the CERT advisory for vendor-specific firmware update guidance.

Workarounds

• Enable BitLocker or LUKS with TPM-bound keys so that PCR changes from firmware tampering invalidate disk decryption
• Require firmware administrator passwords and disable booting from removable media in BIOS setup
• Apply Windows Defender Application Control or Linux Integrity Measurement Architecture (IMA) policies to constrain post-boot code execution

# Verify Secure Boot state and apply dbx update on Linux
mokutil --sb-state
sudo fwupdmgr refresh
sudo fwupdmgr update

# Verify Secure Boot state on Windows (PowerShell, elevated)
Confirm-SecureBootUEFI
Get-SecureBootPolicy